Carb-Light Diet Helps T1D Patients Achieve Glycemic Control

'Very low-carbohydrate diet' of less than 50 g per day

Among people with type 1 diabetes, following a very low-carbohydrate diet (VLCD) can aid in achieving glycemic control, researchers suggested.

Responses from an online survey of people with type 1 diabetes found that those who followed a VLCD reported very good glycemic control -- a mean HbA1c of 5.67% ± 0.66%, according to the study by Belinda Lennerz, MD, PhD, of Boston Children's Hospital, and colleagues. Overall, 97% of these participants achieved the recommended glycemic targets of the American Diabetes Association.

The average blood glucose levels among the subset of patients who reported these values were 104 ± 16 mg/dL, the researchers reported in Pediatrics.

Followers of this diet also noted very few adverse events, with only 2% of the total respondents reporting a diabetes-related hospitalization within the past year -- 1% for ketoacidosis and 1% for hypoglycemia.

Following a switch from a regular diet to the VLCD, participants reported an average change in A1c of -1.45% ± 1.04% (P<0.001). There was also a roughly 0.1% increase in HbA1c for every 10 grams of additional carbohydrates consumed.

"The source and amount of carbohydrates consumed affect postprandial hyperglycemia and glycemic variability more than any other dietary factor, providing a conceptual basis for interest in carbohydrate-modified diets for T1DM," Lennerz et al wrote.

The survey included 316 responses from both adults with type 1 diabetes and the parents of children with type 1 diabetes. These individuals belonged to a Facebook group of people living with type 1 diabetes who adhere to a VLCD. While a VLCD is usually defined as ≤20 to 50 g per day of carbohydrates or ≤5% to 10% of daily caloric intake, the mean carbohydrate intake of these respondents was 36 ± 15 grams per day.

The participants were confirmed as having a positive diabetes antibody test result, a diagnosis of diabetes prior to the age of 20, and a body mass index (BMI) under 30 for adults or lower than the 95% percentile for children. The international cohort included individuals from the U.S., Canada, Europe, and Australia. The findings held similar across pediatric and adults patients.

The pediatric patients' healthcare providers reported that clinical data on the children included in the analysis showed a "marginal decrease" in height following T1D diagnosis: "This possible growth deceleration may have preceded or occurred during the diet and is comparable in magnitude to the previously described decreases in height SDS in T1DM," the researchers suggested, adding that "taken together, these data do not reveal an adverse effect of a VLCD on growth, but additional research into this possibility is warranted."

In an accompanying commentary, Carly Runge and Joyce M. Lee, MD, MPH, both of the University of Michigan in Ann Arbor, praised the study, calling it "an important contribution to the literature." However, they said, a key question that remains is the potential impact the diet may have on pediatric growth, noting that a limitation of the study was the inability to assess pubertal development. Runge and Lee called for a randomized controlled study, to assess not only the effect on HbA1c, but also the frequency of diabetic ketoacidosis, hypoglycemia, BMI, linear growth outcomes, cholesterol, and percentage of time in range.

"Only after the therapy proves efficacious in a trial setting will clinicians have to then tackle the 'barrier' of having patients adhere to this diet."

The study was funded by the National Institutes of Health.

One co-author reported receiving royalties for books on the management of diabetes (which were used by members of the online social media group surveyed for the study). Two other co-authors also reported receiving royalties related to books on low-carbohydrate diets and books on nutrition and obesity in general, and another reported an ownership interest in companies using low-carbohydrate principles. Other co-authors reported financial relationships with Virta Health, Atkins, Merck, and AstraZeneca.

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